Fluid control



March 27, 1945. G. F. FENNO 2,372,417

FLUID CONTROL Filed Sept. 20, 1940 2 Sheets-Sheet 2 We (34 W Patented Mar. 27, 1945 UNITED STATES" PATENT OFFICE 2,372,417

FLUID CONTROL George FrFenn'o, Swarthmore, Pa. Application September 20, 1940, Serial No. 357,605

The proportioning of the feed water input to a boiler to the rate ofsteam outflow and also readjustment of the input to maintain apredetermined level of the water is disclosed in in Patent No. 1,649,342 granted November 1927, and the present invention is an improvementon the means and apparatus disclosed in my previous patent. In the previous patent the various flows and level were translated into electrical impulses and these impulses. were arranged as a Wheatstone bridge to effect the control means. I'have found that much more accurate control can be secured by eliminating the intermediate means and using the fluids themselves to establish the analogue of a Wheatstone bridge but superior in operation.

This invention comprises a fluid control system using a divided circuit branching from a point or points of equal pressure and converging to a" point or points of lower equal pressure andin which the pressure at some selected point in one branch is initially and manually set equal to the pressure of a selected point in the other branch and utilizing any deviation fromthis balance due to flow in the respective branches to position a flow control means. to re-establish the balance, and means for adapting this control whereby it can co-act with one or more additional primary ofltake pipe, divergent and convergent branches interposed in the feed pipe and constituting a parallel connection, conduitsfrom points in the respective branches to the respective sides of the diaphragm, the pressure at said points being normally balanced by the flow resistanc of the respective branches, a boiler interposed at one of said' points in one of said branches and from which steam is drawn in varying quantity thereby unbalancing the pressure between said points and on opposite sides of thediaphragm and operating the feed water valve in consonance with the steam output, the rate of .flow of water through the other branch being changed, thereby changing the pressure on the other side of the diaphragm and restoringthe balance, with or without a water level responsive deviceand connections modifying the action of the diaphragm valve.

The invention also comprises the improvements to be presently described and finally claimed.

17 Claims. (0]. 122-451) be I In the iollowing description reference will-be made to the accompanying drawings forming part hereof and in which:

Figure 1 is "a diagrammatic view illustrating the construction and operation of features of the invention. 1 1

Figure 2 is a similar view illustrating the application of the invention to a steam boiler.

' Figure 2A is a modification of a detail.

Figure 3 is a view illustrating a modification,-

and

Figures 4 and 5 are viewsillustrating other modifications. a In the drawings I is the drum of'a steam generator 'with th fluid level at elevation 2. The fluid "supply enters through the pipe 3, flows through control valve 4, shown as of the well known pilot valve and piston relay operating type, then through an economizer 5 into the boiler where aiter passing through the boiler tubes (not shown) the steam is releasedin a drum. The steam then passes out through super-heater 6 into the pipe 1 where it is distributed for use.

At some point on the down stream side of control valve 4 some of the water is .tapped off, passing through strainer 9, through line l0 containing adjusting valves H andlZ, entering the steam line at point l3. Line 10 is usually very'small pipe, passes only a small amount of water and. most of the drop in pressure from point 8 to, [3

is taken care of by the resistance of the pipe itself.

In case it is found objectionable to introduce the water directly into steam pipe-1, pipe I0 can discharge into a supplemental chamber l4, connected directly to pipe 1 and having the same pressure. The water from chamber I4 is discharged by trap l5, preferably of the continuous discharge orifice type through pipe I6. From a point 32 in line 10 between the valves II and I2 I take ofi another pipe H which applies pressure to oneside of a diaphragm l8, which on the other side has drum pressure applied by means of the reservoir H] which always maintains a constanthead of fluid, in the pipe 20. 'Adjustable spring 51 corrects for static head on the two sides of diaphragm I8. Any difierence in pressure on the two sides of diaphragm 13 causes it to move and by means of rods and levers 2| imparts movement to the pilot valve 24 which admits fluid pressure from a supplementary source through inlet 28 into cylinder 25 which contains a piston connected to valve stem 26 moving valve plunger 21 so as to adjust the flow of fluid from pipe 3. The operating fluid from the pilot valve and power cylinder is discharged through connection 29.

The operation of the apparatus is further illustrated in Fig. 1 in which the various fluid circuits are laid out as in an electrical Wheatstone bridge, the various parts corresponding to the actual apparatus as shown inlFig. 2. Valves II and I2 are so adjusted that the pressure at the point 32 equals the pressure in the drum I. If the steam output of the boiler increases, there will he an increased drop in the fluid pressure through superheater 6, but inasmuch as it is customary to maintain the pressure in steam line I constant, this means that the pressure in the drum I will be increased, because increase in steam output necessitates increase in the rate i combustion in the furnace brought about either manually or automatically (according to common practice and which forms no part of this. invention) with consequent increase in steam pressure in the, drum.

The increase in drum pressure immediately unbalances the pressure on diaphragm. [8-, startingthe valve 4* to open, raising the pressure at point 8 and also at. point 32: until valve 4. openedsuificiently to raise the pressure at point, 32.- to equal the new pressure; in the boiler drum. When this occurs. the diaphragm t8 will. return. to. its

neutral position, causing the. pilot valve 2.4 to be at neutral, which means that. it is neither admitting nor discharging the auxiliary operating fluid from either.- sideof the power piston and plunger 21 will stop at a new position so that the pressure at. 8, will then be such. that the pressure drop. throughthe four legs. of the fluid Wheatstone bridge. will be in the same proportion under the newconditions that. they were under the previous conditions, which. means, that the flow of water through economizer 5 will, under the new conditions. bear the same, proportion to. the flow of steam throughsuperheat'er 6. asithey were under the, first. set of conditions, and. therefore the flow through. 5. will. always. be proportional to. the, flow. through 6; in other words, the. water. input will equal the steam output.

The supply line 28' and. discharge line 29.. are provided with throttle valves so that the admittance and discharge. of operating fluid to the power cylinder which has considerable volumetriccapacity, can be controlled. so that the rate of movement of the main control valve 21 can be made slow enough giving time for the pressure at points. 8' and 32 to change before the plunger 2-!- makes a full stroke, thus preventing hunting.

The pressure at the point 8 includes the static head of the boiler water-level, thus any variation from the normal level will tend to correct itself. For instance, referringto'Figs; 1 and 2a decrease in steam output always means lowerpressure indruml in reference to point 32; therefore; the

apparatus is arranged so that when diaphragm l8 has lower pressureon: the underside-it tends to closefeed control valve- 4, but. if the water level in the drum is above normalthepressureat point 8.: and therefore point 32-. ishigher, it;a1scmovesdiaphragnil.8i downward tending tolcl'osa valve; 4,;whichis; what; is required: to re establish normal water; level.

On team genera rswhioh are not provided with economizers or superrheaters anequivalent. resistance can be introducedinto the water inlet line or the steam, outlet line by. means of. an. orifice or, valve in. the. respective lines.

If. valves. H and 12. are so. adjusted that the frictional resistance from 32 to I3 is made slightly less than through super-heater 6 and the frictional resistance from 8 to 32 is slightly more than the frictional resistance through economizer 5, the pressure at point 32 is lowered relative to the pressure in the drum l and diaphragm l8 will so move control valve 4 that it will slightly overfeed until a higher level of water in drum l raises pressure at point 32 again to bring diaphragm. I8. bacl:v to neutral. 3

As the drop in pressure through both branches varies as the square of the flow, if valves II and [2. are biased as described in the preceding paragraph, the fiow will tend to reduce the pressure at point 32 relative to I as the load increases and av still higher water level in drum 1 will be required' to restore the pressure at 32, either by the static head: orthe co-acting level responsive means, thus giving a higher level at high ratings and a lower level at low ratings, or if point 32 is-biased'in the-opposite direction a reverse characteristic of lower level. at high ratings and a: higher level at. low rating, can be secured. This flexibility is; very desirable as some boilers. operate betterwiththefirst characteristic and some better with the: second.

On; boilers where the pressure drop through the economizer and super-heater are high the static. head due to. changes in water level is's0me-' times-not of, suflicient magnitude.- to give adequate correction as, described. above and. a. more powerful and positive level responsive device such as thermostat 33. in Fig. 2 is required in which the movement of lever 3.4- moves in; consonance with water level. Thermostat 3.3 per seforms-no part of this invention and any of the other well known level responsive devices, could be substituted therefor. Strut 4:0 which can be connected to.- any of the holes inv lever 34. to vary the. sensia tivity, is connected toilever 35pivoted at, point. 36, and. by means: of rod, 31, is, connected to valves H. and I2 in. such a manner that: its movement closes, one. valve and opens the other. .Turna buckles. provide for relative. adjustment of valves.

II and; I2. Fulcrum 3.6 is attached to, the. end of adjusting screw passing through a fixed block, and. is provided.- with hand wheel 53 which permit. of biasing; point; 32. as, described above, and alsofor manually controlling valve 4 for quick filling (13f boiler or forv securing a. quick change. inwater eve Under. automatic control the. movement. of lever 34 and consequently. valves It and i2 biases. point, 32. and. causes either overfeeding or underfeeding as the case. may require until the water level. is. restored. to normal, when lever 34 then restores valves H. and I2: tonormal setting.

Thereis usually somerhythmic surging of. the water level in. a. boiler which does not affect. the average level. and ity is not always advisable to have. thelevel. corrective element .respond. to. these. small, increments. The diaphragm l8 b z-keeping. water flow equal to. steam. flow will usually maintain. the level sufflciently accurate and action of water level. responsive element need not be applied. until" water level. changes beyond some; predetermined limits. For this method of operation, instead. of. connecting rod. 40* directly tolever 35' it can. pass. through. a hole insaid; lever and adjustable collars attached. torod 40. allowing, some movement of. lever 40 beforeinfluencing setting ofvalves M. and I2 (Fig. 2A)

Pressure gauge shows pressure at point 32. and. gauge. 56. shows. drum. pressure. These. two pressurev gauges are. useful. for. securing any de mo'stat 33 in Fig. 4.

gree of bias or for' restoring valves II and I2 'to normal position after using manual control wheel 53. As pipes I and I! are very small they can be brought down to someconvenient point as the main panel board where all adjustments can be readily made as hand Wheel 53 and gauges 55 and 56 would be approximately at the same location. Supplementary valves can be placed in series or parallel with II and I2 permitting of adjustment from more than one location.

With zero boiler output, pressure at points 8, I, I3 and 32 would be the same, except for difference in statichead, therefore movement of valves II and I2 as :shown in Fig. 2 would not change the pressure relations; however the arrangements shown in Figs. 4 and 5 will insure water level response of the control valve at all ratings from zero to maximum.

In Fig. 4 strut 40 is not connected to valves I I and I2 but passes through a hole in lever 2| and has a spring vertically adjustably attached to strut 40 at point 42 and can bear on the upper side of lever 2!. Also a spring is attached to strut 40' at point 44 and can bear against lever 2I' from below. Space between the springs may be provided to allow a certain amount of move ment of lever 2I before it contacts the springs. If the water level is too low, the tube in thermostat 33 will expand and weight 45 will pull lever 34 and strut 40 downward causing the upper spring to put pressure on top of lever 2| in pro-' portion to the amount of deviation of level from normal. This would tend to move diaphragm I8 upward causing valve 4 toopen more until the water flow increases the pressure at points 8 and 32 sufficiently to apply enough pressure through connection I! to top of. diaphragm I8, to restore pilot valve 24 to neutral position, leaving valve 4 in amore open'position, however, as soon as water level is restored to normal by this overfeeding, thermostat 33 will relieve the pressure on springs 4| allowing diaphragm I8 to operate on normal balanced flow control.

The arrangement in Fig. 5 operates the same as Fig. 4 except that thermostat 33 is replaced by a second diaphragm 46 responsiveto-level in drum I. Under side of diaphragm 43'is subject to steam pressure plus a constant. head by means of pipe 41 connectedto reservoir I9. The upper side of diaphragm 46 is connected to near the bottom of the boiler drum I by pipe 48 and is subject to a variable pressure due to height of water in drum I and to steam pressure.' By means of lever 50 and link 5| diaphragm 45 is connected through springs to lever 2|. Diaphragm 46 is larger than diaphragm I8 as the variations in pressure on it due to changes in water level are much smaller than the variations in pressure across diaphragm I8. By varying the pressure on lever 2I diaphragm 4B accomplishes the same result as ther- Water level responsive diaphragm 46 can be substituted for thermostat 33 in Fig. 2, lever 50 replacing lever 34. V

,In Figs. 4 and 5 valves II and IZ are theoretically not necessary because on referring to Fig. 1 it is evident if vpoint 32 is so selected that the drop from 8 to 32 equals the drop through5 and the drop from 32 to I3 equals the drop through 6 the flow ratios willbe correct, but practically it is difiicult to so select point 32 in pipe III that the above conditions exactly occur and therefore valves II and I2 make itpossible to easily correct for any error in selection of location of point 32. .Also valvesl I andIZare valuable for biasthe change in inlet pressure;

ing and manual control and preferably are linked together for operation by means of hand wheel 53.

The Wheatstone bridge principle of fluid control is unique in that its successful operation does not depend on maintaining any fixed differential in. pressure either between the header which supplies water through pipe 3 and the boiler drum, or across the flow control valve 4. For instance if the boiler were operating at a constant load with a given setting of valve 4 and there is an increase in pressure from the boiler feed pump at point 3, there would be an increase in pressure at point 8 and therefore at point 32, but there would be no. increase in pressure at drum I, which pressure is entirely dependenton the output 'of steam. Therefore under this assumed condition the diaphragm I8 would move and cause pilot valve 24 to re-position control valve 4, until the flows in 5 and 6 are again equalcausing. the ratio of the pressure drop Stol lto13 to be the same as before the change thus bringing pressure at point 32 back to pressure in I and the pilot would return to neutral,- locking valve 4 in the new position-to compensate for This feature is very desirable as many plants use constant speed motors for driving centrifugal boiler feed pumps, which pumps have difierent discharge pressures for different outputs of water. The present invention thus eliminates the many devices which are expensive and none to accurate for maintaining a fixed or a variable differential pressure between two points in the main system, and which in addition to the pressure control means require an additional control means responsive to fluid level or flow or both while this invention affords complete fluid control with the use of only one control valve. I

The diaphragm I8 can of course be replaced by any pressure responsive device, such as a tilting mercury U-tub'e, or a submersible pressure bell,

loaded controlled by fluid pressure which may be varied by the position of diaphragm I8.

It will be obvious to those skilled in the art that modifications may be made in details of construction and in matters of mere form without departing from the spirit of the invention.

I claim: v

1. An automatic feed water regulator for steam boilers comprising the combination of a boiler, a feedwater inlet, a steam outlet, branches divergent from the inlet and then convergentto the outlet and constituting a parallel connection of which one branch is adapted to vary the pressure drop relation of the branches in response to flow through it governed by valve movement, and

tot level and which. modify the: response of the pressure responsive apparatus.

3; An automatic feed water regulatorior steam boilers substantially as described claim 1,; in combination with means responsive to broiler water level.v and including lost motion. mechanism and which modifies the response of the pressure apparatus; above and below predetermined limits 4. automatic feed water regulator for steam boilers substantially as described in claim L, link-- age interposed between the pressure responsive device and. the feed water valve, a thermostatic. water level device and connections. from the waher level device to the linkage: for modifying theaction of the-- pressure device.

5.. An automatic feed waterregulatcrfor steam boilers comprising the combination of a boiler, a feed: water valve having a, pilot valve and piston relay for operating it, a feed v water inlet, a steam outlet, branches divergent from the inlet. and then convergent to the outlet and constituting a parallel connection of which one branch is adapted to vary the pressure drop relation of the branches in response to flow through it governed by feed water valve movement and of which the other branch includes the boiler and is adapted to varythe pressure drop relation of the' branches in response to steam flow through a part of said other branch due to boiler demand, pressure responsive apparatus directly connected across said branches" and responsive to the balance and unbalance of the pressure drop relation in the branches and connected to the pilot valve to control the position of the feed water valve.

6. An automatic feed water regulator for steam boilers comprising the combination of a boiler, a feed water valve having a pilot valve and piston relay for operating it, a feed water inlet, a steam outlet, branches divergent from the inlet and then convergent to the outlet and constituting aparallel connection of which one branch is adapted to vary the pressure drop'relation of the branches in response to flow through it governed by feed water valve movement and of which the other branch includes the boiler and is adapted to vary the pressure drop relation of the branches in response to steam flow through a part of said other branch dueto boiler demand, pressure responsive apparatus directly connected across said branches and responsive to the balance and unbalance of the pressure drop relation in the branches and connected to the pilot valve-to control the position of the feed water valve, and means responsive to boiler water level and which modify the response of the pres sure responsive apparatus.

7. An automatic feed water regulator for steam boilers including a.- diaphragm controlled inlet valve and a steam oiitake pipe, branches divergent from the inlet valve and then convergent to the oiitakepipe and constituting a parallel con-- nection between the outlet side of the valve and the. steam pipe, a boiler interposed in one; of said branches and having a connection to one side of the diaphragm oi the valve, a connection inter-- posed in the other branch tothe opposite side of the diaphragm, there being interposed in the last mentioned branch flow control valves, said coristruction providing two legs in each branch, the normal flow in each branch providing substantially the same pressure drop at the junctions of the respective legs, a change in flow in the legconnecting the boiler to the steam pipe unbalancing the pressure. on the faces of the diaphragm, and actuating said valve which. thereare-7am? aiter changes the rate of flow in another leg and balances the pressure at the other side of the diaphragm thereby makin the water input balance the steam output.

8.. A flow control systemv comprising branches connected. at the same point of common inlet: and at the same point of. common outlet, means for supplying liquid to said point. of common. inlet, flow controlled means located in. one of said. branches by which the initial pressure at some selected point in this firstbranch. is manually set either above or below the. pressure established at a selected point in the other or second bramch at a, point where the liquid is changed to a gas, flow controlling means located at. the common inlet to the branches and positioned by bringing these two points into balance which causes theflow on the inlet side of the second branch to become progressively higher or lower than the flow on. the outlet side of the second branch, and an additional primary control responsive to the level of the liquid which is changed to gas and means for connecting said additional primary control to the flow controlling means for the first branch thereby varying said ratio.

9;. A flow control system comprising the com.- bi-nation of a fluid bridge operating on the Wheatstone principle, a liquid. flow control means operaiivelyconnected to the bridge and located at the entrance of its branches, one or: more: valves located in a'branch of the fluid bridge for establishing. pressure relations in the bridge, a. vapor generating. means located in the other branch. of the bridge which unbalances thebridge, and means responsive to the balance i. e.,

equal pressure at.- selected points in each branch; and unbalance i. e.., unequal pressure in thebranches at saidselected points; of the bridgedue to flow, said last named means positioning the flow control means.

10. An automatic. feed water regulator for steam boilers comprising the combination. of a feed water valve, a fluid bridge operating on the- Wheatstone principle, one leg of which includes means for changing av liquid to; a gas thereby un-- balancing the bridge, i; e., causing unequal pressure in the branches of the bridge, means actuated by the fluid in the. bridge and responsive to the balance: 1.. e., equai pressure at selected points in each branch, and unbalance i, e., unequal pressure in the.- branches at said selected points, of the. bridge and controlling the position of said. valve which supplies: liquid to the Wheatstonebridge;

11 An automatic: feed water regulator forsteam boilers comprising the combination of a boiler, a feed water: valve for the:- boiler, a fluid .bridge operating. on; the Wheatstone principle,

means: actuated by the fluid m the bridge responsive to the balance i.. e: equal pressure at selected points in each branch, and unbalance i. e.. unequal pressure in the branches at said selected points, of the bridge and controlling the position of said valve, and devices responsive to boiler water level: and which modify the action of said meansin respectto. the positioning of said valve, said boiler locatedin part of the bridge, and: said valve located at the entrance of the. bridge;

12 ,111. an. automatic feed water regulator for steam boilers the combination of a. boiler, a feed water valve, a; fluid. bridge operating. on the Wheatstone principleand through a. part of: one leg. of which steam passes from the boiler, and

apparatus actuated by. the fluid in the bridgeand responsive to changes in balance of the bridge 1. e. the changes in the difierential pressure in the cated at the entrance of the bridge.

13. In an automatic feed water regulator for steam boilers the combination of a boiler, a feed water valve, a fluid bridge operating on the Wheatstone principle of which one le includes the boiler and through a part of which leg steam passes, apparatus actuated by the fluid in the bridge and responsive to changes in balance of the bridge, i. e., deviation from equal pressure at selected points in the respective branches, for automatically maintaining a fixed ratio between water input and steam output, said apparatus operatively related to said feed water valve, said feed water valve located at the inlet to the branches of said bridge, and a boiler water level regulator responsive to changes in water level, a connection between the water level regulator and the feed water valve which positions the latter thereby modifying the relative values of the pressures at the selected points.

14. A flow control system comprising a water o inlet, a steam outlet, branches divergent from the inlet and then convergent to the outlet and in which the pressure at some selected point on one branch is set by flow control in that branch equal to the pressure established at a selected point in the other branch of the circuit by flow variation, a steam generator in said other branch, and flow control means at the inlet of the branches and positioned by apparatus arranged to be responsive to any deviation from the equality of pressures in said branches due to change in flow,

said last named means and apparatus operated to re-establish the equality of pressures in said branches. V

15. A fiowcontrol system comprising a water inlet, a steam outlet, branches divergent from the inlet and then convergent to the outlet and in which the pressure at some selected point on one branch is set by flow control in that branch equal to the pressure established at a selected point in the other branch of the circuit by flow variation, a steam generator in said other branch, flow control means at the inlet to the divergent branches and positioned by any deviation from the balance due to change in flow to tend to re-establish the balance, and an additional primary control responsive to liquid level in said steam generator, a connection between the additional primary control and the flow control means which positions the latter thereby modifying the action-of said flow control means. i

16. A flow control system comprising the combination of, a fluid bridge operating on the Wheatstone principle, a liquid flow control means operatively connected to the inlet to the bridge, one branch of the fluid bridge proportioned for establishing the pressure relations in the bridge, a vapor generating means located in the other branch which unbalances the bridge, and means responsive to the balance, 1. e., equal pressure at selected points in each branch, and unbalance, i. e. unequal pressure in the branches at said selected points of the bridge due to flow, which positions the flow control means.

17. A flow control system comprising, branches connected at the same point of common inlet and at the same point of common outlet, liquid flow control means in the first of said branches by which the initial pressure at some selected point is manually set less than the pressure established at a selected point in the second branch at which the liquid is changed to a gas, fiow controlling means located at the common inlet to the branches, means for positioning the last-mentioned control means by the difference in pressure between the selected points, and a regulator responsive to fluid level at the point where the liquid is changed to a gas having lost motion connection for modifying the pressure at the selected point in the first branch which causes the flow, i .e., weight per unit of time, on the inlet side of the second branch to become greater than the flow, i. e., weight per unit of time, on the outlet side of the branch.

GEO. F. FENNO. 

